For examination of tissues taken from a living organism, for pathological diagnosis of the tissues, and for morphological study in a tissue laboratory, the biological tissues are ordinarily placed in a cassette, fixed, embedded and sliced. More specifically, tissues taken from a living organism are directly put in a bottle containing a fixing agent to fix the tissues. Alternatively, tissues are put in a nylon mesh bag first and then the nylon mesh bag is put in a bottle. Further alternatively, tissues are put in a cassette 1 formed of a porous plate as shown in FIG. 17, its lid (not shown) is closed, and the cassette is put in a bottle containing formalin, pure ethanol or acetone.
In FIG. 17, numeral 2 indicates partitions provided in the container, numeral 3 indicates numerous small holes formed in the bottom of the container, and numeral 4 indicates a slot in which the lid of the cassette is fitted. With biological tissues received, the container is carried to a tissue laboratory. Otherwise, fixed biological tissues are sometimes placed in a new cassette and subjected to the following processes. In the laboratory, for tissues that are placed in a cassette and fixed, the lid of the cassette is opened to check the biological tissues inside and the patient information displayed on the cassette, the lid is closed, and the cassette is set in an automatic embedding device. For smaller biopsy tissues, since they are rarely put in a cassette from the beginning, they are usually transferred from the fixing bottle into a cassette for small tissues at this stage.
For biological tissues that are not put in a cassette but immersed in a fixing solution in a fixing bottle, after the tissues in the fixing bottle have been transferred into a new cassette, the cassette is set in an automatic embedding device. Tissues in a nylon mesh bag can be set in an automatic embedding device as it is. In the automatic embedding device, the tissues in a cassette or in a nylon mesh bag are subjected to dehydration and paraffin infiltration. Upon completion of paraffin infiltration, the cassette or the nylon mesh bag containing the tissues is removed from the automatic embedding device, and transferred into a paraffin tank in an adjacent embedding center. An automatic embedding device automatically carries out series of processes from dehydration to paraffin infiltration.
The embedding center is a device for embedding and cooling tissues infiltrated with an embedding agent. Today, in most laboratories, an automatic embedding device and an embedding center are used. But a cassette containing biological tissues may be manually subjected to dehydration and paraffin infiltration, without using an automatic embedding device. Also, the embedding and cooling steps may be carried out manually without using an embedding center. Then, a separate embedding dish is set on a table in the embedding center, and a small amount of molten paraffin is poured into the embedding dish.
Biological tissues are removed from the cassette or nylon mesh bag taken out of the paraffin tank in the embedding center with tweezers, and set in the embedding dish. An embedding frame is then placed on the embedding dish, molten paraffin is poured into the dish from above, and the embedding dish including the embedding frame, which has now become integral with the biological tissues, is placed on a cooling station adjacent to the embedding center to cool it. When the paraffin solidifies, the block comprising the now integral biological tissues and embedding frame is removed from the embedding dish. The block is set in a microtome and sliced. This conventional fixing, embedding and slicing method is described in Patent document 1, too.    Patent document 1: JP Patent Publication 8-211047A